1. Field of the Invention
The present invention relates to a resource allocation method, and more particularly, to a resource allocation method in a PCA period according to MBOA MAC for performing resource competition between protocols based on a protocol in a home network environment using multiple protocols.
This work was supported the IT R&D program of MIC/IITA. [2006-S-071-01, “Development of UWB solution for high speed multimedia transmission”]
2. Description of the Related Art
As various protocols are simultaneously supported in a home network environment, a multi-band OFDM alliance MAC (MBOA MAC) receives attention.
In data communication using MOA MAC, a super frame is used as a basic unit. For example, if one super frame is for 65000 micro seconds, a super frame is repeated at every 65000 micro second, and all type of data communication is performed at every each super frame.
FIG. 1 is a diagram illustrating a structure of a super frame.
Referring to FIG. 1, one super frame is configured of two parts. One is a beacon period for transmitting a beacon frame for synchronizing and managing a network formed by MBOA MAC. In the beacon period, normal data is restricted to transmit, and only beacon frames are exchanged. The other is a data period. The data period is divided again into a distributed reservation protocol (DRP) period reserving and using resources without competition, and a prioritized contention access (PCA) period using resources through competition.
In the PCA period, when external devices are request resources, the external devices are classified by priority based on data type of the resources, and the external devices are forcedly given a discriminated idle time according to the priority for resource competition.
FIG. 2 is a diagram for describing a step of using resources through competition in a PCA period according to MBOA MAC.
Referring to FIG. 2, an arbitration inter frame space (AIFS) value is allocated to each of the external devices requesting resources. The AIFS value assigns an idle time to the external devices for letting the external device in an idle state before competing with other devices for resources. Therefore, all devices requesting the resources to use try to use corresponding resources after being idle as long as the AIFS value.
A priority deciding the AIFS value is defined by data type of resources requested by a device. Generally, it is divided into four categories. Such a classification is an access category.
FIG. 3 is a diagram illustrating an AIFS value defined for an access category according to a data type in a conventional MBOA MAC.
As shown in FIG. 4, four categories are AC_VO denoting voice data, AC_VL denoting video data, AC_BE denoting best effort data, and AC_BK denoting background data. In MBOA MAC, a device using an access category having a higher priority has a shorter AIFS time than a device having a lower priority. As shown in FIG. 3, since the video data has a higher priority than the background data, the video data has a shorter idle time than the background data. A device using data having a higher priority has a shorter idle time than a device using a data having a lower priority. Since a device having a shorter idle time tries to acquire resource after short idle time, the device using the data with higher priority has a large probability to win the competition.
It expects to use multiple protocols in a future home network environment instead of using a single protocol. Recently, there are many researches in progress for developing a method of simultaneously using multiple protocols such as IEEE 1394, USB, Bluetooth, and UPnP. A conventional PCA method is ineffective for multiple-protocol environment because it uses a method of competition based on data type which is effective in a single protocol environment. For example, when two protocols IEEE 1394 and USB using same data type are provided simultaneously, it is difficult to guarantee to give a priority to an application using the IEEE 1394 in a competition with an application using the USB protocol if same data type is used although the application using the IEEE 1394 protocol has higher priority than a PC application using USB protocol because the application using IEEE 1394 protocol is generally used in an AV device handling mess capacity multimedia.